Referring to the meeting during a visit to Pakistan, the US Secretary of State said: "We're not in any kind of negotiations. We've had one preliminary meeting just to see if they would show up."

She added: "We are going to continue fighting where necessary to protect our interests, and so are the Pakistani military because you cannot allow terrorists to gain ground. But we are also open to talking. We have reached out to the Taliban, we have reached out to the Haqqani network to test their willingness and their sincerity."

Mrs Clinton did not disclose the location of the meeting, which was suggested and arranged by Pakistan's ISI secret service and came amid secret talks with representatives of the Taliban.

Both efforts have proved futile. Within weeks of the meeting the US was blaming the Haqqani clan for two large attacks in Kabul, a truck bombing that killed five Afghans and injured 77 Americans, and a 20-hour gun battle around the US embassy an Nato compounds.

As relations with Islamabad deteriorated, Adm Mike Mullen, then the top US military officer, called the Haqqani network a "veritable arm" of the ISI, and Washington sanctioned numerous drone attacks on its strongholds in North Waziristan, an autonomous region of Pakistan.

Mrs Clinton, at the conclusion of two days of talks in Afghanistan and Pakistan designed to hasten an end to the 10-year conflict, said that "we do not see any contradiction" between fighting and talking.

Accompanied by David Petraeus, the CIA director, and Gen Martin Dempsey, the chairman of the joint chiefs of staff, she urged Pakistan to take action within "days and weeks" on dismantling Afghan militant havens.

Pakistan has so far refused to open a new offensive against the Haqqani network, arguing that its troops are too overstretched and that the country has already sacrificed too many lives fighting the Taliban and Pashtun militias elsewhere in its tribal zones.

In response, Hina Rabbani Khar, Pakistan's foreign minister, gave only a lukewarm commitment to do more.

"Do safe havens exist? Yes, they do exist both sides. Do we need to co-operate? Yes. We can co-operate more and achieve better results," she said.